With the addition of conventional and draped aerial photography, infrared photography, and artificial aperture side-looking radar, the total information available to ERTS exceeded two million images, with new input on the order of thirty images an hour. All this information had to be catalogued, stored, and made available for instantaneous retrieval. ERTS was like a library which acquired seven hundred new books a day. It was not surprising that the librarians worked at fever pitch around the clock.

Visitors to ERTS never seemed to realize that even with computers, such data-handling capacity would have been impossible ten years earlier. Nor did visitors understand the basic nature of the ERTS information-they assumed that the pictures on the screens were photographic, although they were not.

Photography was a nineteenth-century chemical system for recording information using light-sensitive silver salts. ERTS utilized a twentieth-century electronic system for recording information, analogous to chemical photographs, but very different. Instead of cameras, ERTS used multi-spectral scanners; instead of film, they used CCTs-computer compatible tapes. In fact, ERTS did not bother with “pictures” as they were ordinarily understood from old-fashioned photographic technology. ERTS bought “data scans” which they converted to “data displays,” as the need arose.

Since the ERTS images were just electrical signals recorded on magnetic tape, a great variety of electrical image manipulation was possible. ERTS had 837 computer programs to alter imagery: to enhance it, to eliminate unwanted elements, to bring out details. Ross used fourteen programs on the Congo videotape-particularly on the static-filled section in which the hand and face appeared, just before the antenna was smashed.

First she earned out what was called a “wash cycle,” getting rid of the static. She identified the static lines as occurring at specific scan positions, and having a specific gray-scale value. She instructed the computer to cancel those lines.